Contamination of soil and drainage water by toxic heavy metals is
one of the most serious problems in agriculture. This was strikingly illustrated in the
1980s in the San Joaquin Valley, when extraordinary levels of selenium led to death
and embryonic defects in migratory birds and other wildlife. The selenium, a naturally
occurring element that leaches into the subsurface drainage water in certain geologic
areas, was the result of years of agricultural drainage in the valley.

Because of extraordinary cleanup costs, real-world solutions to such contamination
have been elusive. This spring, however, researchers at the College’s Department of
Plant and Microbial Biology, the U.S. Department of Agriculture (USDA), and Colorado
State University proved the concept that plants genetically engineered to tolerate
and remove heavy metals can get the job done. “The principle is to extract pollutants
through the plant roots, harvest the shoots, and carry them away from the site for
safe disposal,” says Professor Norman Terry, coauthor of the study. “These plants
could clean up huge acreages of soil, easily and inexpensively.”

In their study, the researchers modified Indian mustard plants to produce greater
quantities of certain enzymes that regulate how much selenium (in the form of selenate)
gets taken up by the roots. Earlier studies had proven the technique in laboratory
and greenhouse experiments, but this study, published in the journal
Environmental Science and Technology, showed it to be successful under actual field
conditions. Their results showed a 430 percent increase in the amount of selenium
accumulated in the transgenic mustard shoots as compared to wild-type plants.

Because genetically engineered strains of a given plant can cross-pollinate with wild
types of the same species—and may pose risks to other populations within an
ecosystem—the fieldwork was subject to stringent precautions. Researchers
exhaustively documented the function of each genetic alteration, the different characteristics
of the transgenic and wild type mustard plants, and all potential interactions
between the host plants and other species within the ecosystem.Wildlife was
fenced out of the test plots, and the harvest of the plants was timed to preclude any
possibility of cross-pollination. In addition, the study was closely monitored and
videotaped by USDA inspectors.

“The regulatory hurdles can make this type of research difficult to pursue, but they
represent legitimate concerns that we need to address,” Terry says. “In the end, the
clear benefit is developing new technologies that clean up the environment.”